If you do any work at all involving the internal electronics in guitars or basses, sooner or later you’ll probably need to solder a ground connection to the back of a potentiometer (volume or tone control). This procedure should help:
1. Sand or scrape the metal surface of the back of the pot to rough it up.
2. Heat the potentiometer – don’t wait too long, as excess heat can damage a pot.
3. Melt a drop of solder on the pot – again, don’t overheat the pot, but the solder needs to flow, not just glob onto the pot surface.
4. Tin the wire.
5. Lay the wire on the solder on the pot. Press the soldering iron down on the wire just until the solder starts to flow.